I'd like to make PDBSelectors IMP::Objects. The change would not affect python code. For C++ users, PDBSelectors would have to be created with new instead of on the stack. So in general, a call that was read_pdb(name, CAlphaPDBSelector()) would become read_pdb(name, new CAlphaPDBSelector())
The advantages are
- we could now provide AndPDBSelector and OrPDBSelector which work in python
- there aren't annoying corner cases which cause problems due to the selectors being sliced.
Objections?